Systems currently exist that supply therapeutic substances through a medical instrument to regions of a patient's body. Such regions may include a diseased blood vessel, body cavity or organ. In the case of a diseased blood vessel, for example, the therapeutic agent may be used to treat an arterial lesion and/or to promote an angiogenic response.
Medical instruments such as needles and ablation electrodes attached to the distal end of a catheter assembly are used to treat regions within the patient's body. For example, in applying or delivering a therapeutic substance that promotes angiogenesis, a catheter with a needle disposed therein may be guided through the body to the left ventricle of the heart where the needle delivers a therapeutic agent to the left ventricle wall. U.S. Pat. No. 6,120,520, for example, describes a catheter which may be guided through blood vessels in the body to the left ventricle in order to deliver a bioagent into the ventricle's wall. U.S. Pat. Nos. 6,251,104 and 6,102,926 also describe catheters which may be used to guide a treatment device (e.g. a tissue ablation device) through the body and into the left ventricle for treatment of the myocardium.
These types of catheter systems eliminate the need for prior intra-operative procedures, such as a procedure in which the chest cavity is opened to penetrate the heart wall. Intra-operative procedures can subject a patient to prolonged recovery periods and can often lead to further complications. However, there are many difficulties associated with guiding a catheter through the body and introducing the catheter into a particular body cavity or vessel wall. One such difficulty is the maneuverability of the catheter for advancing it through the body while maintaining sufficient strength and rigidity. Often catheters are not shaped adequately for maneuvering through particular portions of the body or to fit a particular body cavity. In addition, catheters are often insufficiently flexible to be maneuvered properly within the particular body cavity.
Another difficulty is maneuvering a medical instrument attached to the catheter to a particular target area in the body cavity. For example, difficulties may arise in positioning the medical instrument within the left ventricular cavity after the distal end of the catheter has extended into the ventricular cavity. The catheter may have sufficient rigidity and strength to be inserted into the body cavity. However, a problem can occur when the catheter is not sufficiently flexible to position the medical instrument to a target site within the body cavity.